FIG. 1 is a schematic view of a structure of an integrated circuit 1 working without contact, mounted for example, on a plastic card 20 to form a contactless chip card. This integrated circuit 1 is provided with an antenna circuit 10 comprising a capacitor 11 integrated into the silicon of the integrated circuit 1 and an antenna coil 12. The antenna coil 12 is mounted on the plastic card 20 and is connected to the terminals of the capacitor 11 by means of connection pads 13 by tin/lead soldering or ultrasonic soldering. The antenna circuit 10 is a resonant circuit whose nominal resonance frequency Fp is generally 13.56 MHz according to prevailing standards. When the antenna coil 12 is placed in an alternating magnetic field Fld locked into the frequency Fp, an alternating voltage Vac appears at its terminals by electromagnetic induction. This alternating voltage Vac could reach 20 to 40 volts under efficient conditions of operation and is converted by a rectifier circuit 14 into a direct voltage Vcc for the integrated circuit.
In general, the antenna coil 12 is not connected to the pads 13 of the integrated circuit 1 except when the integrated circuit 1 is mounted on the plastic card 20 during an advanced stage of manufacturing. The integrated circuit 1 is then covered with a protective resin. At this stage, and despite various controls that may have been planned during the previous steps, occasionally the connection of the antenna coil 12 is faulty, or the integrated capacitor 11 does not have its nominal value. This may be so, for example, because of a drift in the application of the method of manufacture of the integrated circuit. It is therefore desirable to detect these anomalies.